Effects of diquat and fomesafen applied alone and in combination with a nonylphenol polyethoxylate adjuvant on Lemna minor in aquatic indoor microcosms.
The influence of tank-mix adjuvants on pesticide toxicity remains largely unknown. Agral 90, a nonylphenol polyethoxylated tank-mix adjuvant, has been used with diquat (bipyridylium herbicide) and fomesafen (diphenyl-ether herbicide) in aquatic indoor microcosms in order to compare the toxicity of the single compounds and of binary herbicide-adjuvant mixtures to Lemna minor. Twenty-four microcosms were used and treatments were performed with substances alone or with herbicide-adjuvant binary mixtures, at two concentrations levels (44.4 and 222.2 microg/L for the herbicides, and 100 and 500 microg/L for Agral 90). Toxicity was assessed weekly for 1 month through growth measurements, as inferred from the relative frond number (RFN) and relative frond area (RFA). Concentrations of diquat and fomesafen in water and sediments were measured weekly. The herbicides showed very different behaviour in microcosms, with a rapid disappearance of diquat from the aqueous phase whereas fomesafen levels remained almost constant over time. Diquat strongly inhibited the growth of L. minor whereas fomesafen had no effect on plant growth. Presence of the adjuvant only slightly reduced the effect of the lowest concentration of diquat, probably as a result of dispersion of the herbicide at the water surface. It is concluded that tank-mix adjuvant designed to improve herbicide efficiency in the terrestrial environment did not have any effect on aquatic plants when applied to the aquatic environment.
Gorzerino
Caroline
C
INRA, UMR Ecologie et Santé des Ecosystèmes, Equipe Ecotoxicologie et Qualité des Milieux Aquatiques, Agrocampus Rennes, 65 rue de Saint Brieuc, F-35042 Rennes, France.
Quemeneur
Alphonse
A
Hillenweck
Anne
A
Baradat
Maryse
M
Delous
Georges
G
Ollitrault
Martine
M
Azam
Didier
D
Caquet
Thierry
T
Lagadic
Laurent
L
D000277:Adjuvants, Pharmaceutic; D029064:Araceae / Q000187:drug effects* / Q000254:growth & development; D001549:Benzamides / Q000633:toxicity*; D004178:Diquat / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D006540:Herbicides / Q000633:toxicity*; D017137:Nonoxynol / Q000633:toxicity; D013501:Surface-Active Agents / Q000633:toxicity; D018675:Toxicity Tests; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D000277:Adjuvants, Pharmaceutic; D001549:Benzamides; D004338:Drug Combinations; D006540:Herbicides; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical; D017137:Nonoxynol; D004178:Diquat; C088563:fomesafen